1. Field of the Invention
The present invention relates to wireless networks, and in particular to reusing antenna parameters in beamforming and sector antennas.
2. Description of the Related Technology
With the proliferation of high quality video, an increasing number of electronic devices, such as consumer electronic devices, utilize high definition (HD) video which can require multiple gigabit per second (Gbps) or more in data rate, hence high bandwidth for transmission. As such, when transmitting such HD video between devices, conventional transmission approaches compress the HD video to a fraction of its size to lower the required transmission bandwidth. The compressed video is then decompressed for consumption. However, with each compression and subsequent decompression of the video data, some data can be lost and the picture quality can be lowered.
The High-Definition Multimedia Interface (HDMI) specification allows transfer of compressed or uncompressed HD Audio and/or Video (A/V) data between devices via a cable. While consumer electronics makers are beginning to offer HDMI-compatible equipment, there is not yet a suitable wireless (e.g., radio frequency) technology that is capable of transmitting compressed or uncompressed HD video signals. Wireless local area network (WLAN) and similar technologies can suffer interference issues and the bandwidth is not enough to carry the compressed or uncompressed HD A/V data.
Recently, millimeter wave (mm-wave) Gbps communication is becoming a reality with technological advances and regulatory developments. For example, in early 2000, Federal Communications Commission (FCC) allocated a 7 GHz frequency band in the 57-64 GHz mm-wave band (also known as the 60 GHz frequency band) for unlicensed use. Opening of this large frequency band, combined with advances in CMOS technologies, makes it attractive to support gigabit per second (Gbps) wireless applications, such as compressed or uncompressed high definition video streaming and large file transfers.
One of the major challenges for mm-wave Gbps communications is the poor link budget, as a radio signal propagating in the mm-wave frequency band experiences significant path loss, reflection loss and other degradation. Also, the 60 GHz frequency band happens to be in an oxygen absorption band, which means that transmitted energy is quickly absorbed by oxygen molecules in the atmosphere, making the received signal even weaker.
Given the lossy nature of the radio channel as well as the limited CMOS performance at a mm-wave band, Gbps communications becomes very challenging. To improve the link quality, directional transmission is generally preferred. Due to the extremely short wavelength, it becomes possible and beneficial to integrate a large number (e.g., between 10 and 30) of antenna elements into an antenna array package. Antenna array based beamforming thus emerges as an attractive solution, featuring high beamforming gain and electronic steerability. In current practice of 60 GHz communications, a single RF chain is generally preferred for cost reduction consideration. For an orthogonal frequency division multiplexing (OFDM) based system, this implies that conventional digital beamforming which employs independent beamforming vectors across multiple subcarriers cannot be applied. Analog beamforming, which employs the same beamforming vector across multiple subcarriers, are used instead. An improvement in signal-to-noise (S/N) ratio can be achieved by periodically performing antenna trainings in a beamforming wireless system. However, antenna training incurs overhead and delays and reduces channel use efficiency.